Knowledge of body composition changes and nutritional requirements in spinal cord trauma with paraplegia or quadriplegia is limited. We plan to measure lean body mass (LBM) and total body fat as functions of total body water (TBW) and total body potassium (TBK), under controlled dietary conditions. Total body water will be measured with deuterium oxide (heavy water) and bioimpedance and extracellular fluid will be determined with bromide. When stable, patients will be transported to the 40K Body Counter for measurement of TBK. Studies will be performed shortly after trauma with periodic longitudinal evaluation (40K counting) through rehabilitation. To measure changes in muscle protein turnover and muscle wasting, urinary excretion of the amino acid, 3-Methyl histidine, and urine creatinine will be determined. The effect of spinal cord trauma on bone mineral and soft tissues below the neurologic level of injury will be studied by photon absorptimetry and CT scanning. All of these body composition measurement techniques will be complemented by metabolic balance study periods at intervals to evaluate further the quantitative aspects of losses and gains of soft tissues and bone in spinal cord trauma. From all of these data, optimum protein-calorie nutritional support will be defined.